Dielectric materials, or dielectrics, are widely used in semiconductor fabrication processes. Dielectrics may be used for isolating active areas of the wafer from inactive areas, or to isolate conductive features (e.g., conductive lines and vias) located in the same or different layers of a semiconductor device. For example, in the front-end-of-line (FEOL) processing, dielectrics such as silicon oxide, silicon nitride, silicon oxynitride, or the like, are used to form shallow trench isolation (STI) regions to separate and isolate active areas on a semiconductor wafer from each other. As another example, in the back-end-of-line (BEOL) processing, dielectrics are used to form Inter-Layer Dielectric (ILD) layers over a semiconductor substrate and fill the space between the gate stacks of transistors in integrated circuit (IC) devices. Dielectrics are also used to form Inter-Metal Dielectric (IMD) layers over the ILD layers. IMD layers may be formed of a low-k dielectric material having a dielectric constant (k-value) lower than about 3.0, about 2.5, or even lower.
Chemical vapor deposition (CVD) is widely used for forming dielectrics in IC devices and includes many different variations such as Plasma Enhanced Chemical Vapor Deposition (PECVD), Low Pressure Chemical Vapor Deposition (LPCVD), and Flowable Chemical Vapor Deposition (FCVD). In a typical CVD process, precursors are introduced in a processing region, such as a processing chamber. Chemical reactions happen between the precursors and dielectrics are formed over a workpiece (e.g., a substrate). After the dielectrics is formed, a curing process, such as a Ultra-Violet (UV) curing process, may be performed to cure the dielectrics to enhance its chemical and/or physical properties, e.g., to increase its hardness and/or lower its dielectric constant (k value). Challenges and problems exist in the existing UV curing process. New and improved UV curing processes for fabricating semiconductor devices are needed.